patch 9.0.0478: test for 'splitscroll' takes too much time

Problem:    Test for 'splitscroll' takes too much time.
Solution:   Only test some of the combinations. (Luuk van Baal, closes #11139)
diff --git a/runtime/optwin.vim b/runtime/optwin.vim
index 6b9b5fe..f2748b4 100644
--- a/runtime/optwin.vim
+++ b/runtime/optwin.vim
@@ -515,7 +515,7 @@
 call <SID>BinOptionG("sb", &sb)
 call <SID>AddOption("splitright", gettext("a new window is put right of the current one"))
 call <SID>BinOptionG("spr", &spr)
-call <SID>AddOption("splitscroll", gettext("determines scroll behavior when spliting windows"))
+call <SID>AddOption("splitscroll", gettext("determines scroll behavior for split windows"))
 call <SID>BinOptionG("spsc", &spsc)
 call <SID>AddOption("scrollbind", gettext("this window scrolls together with other bound windows"))
 call append("$", "\t" .. s:local_to_window)